A method for fabricating a photomask using a self-assembled molecule layer, comprising: forming, on a transparent substrate, a stacked structure of a phase shift pattern and a light shielding pattern over the phase shift pattern, the stacked structure exposing a portion of a surface of the transparent substrate; exposing the phase shift pattern and a portion of the surface of the transparent substrate by removing a portion of the light shielding pattern; forming a self-assembled molecule layer allowing movement of electrons on the exposed surface of the transparent substrate; measuring a critical dimension of the phase shift pattern formed with the self-assembled molecule layer; neutralizing electrons applied during the measurement of the critical dimension with the self-assembled molecule layer allowing movement of electrons; and removing the self-assembled molecule layer.